Quantifying the quality and connectivity of sidewalks: walking accessibility indices

By Saumya Jain
The May 2019 issue of the Institute of Traffic Engineers journal was focused on healthy and sustainable transportation solutions. With the constant rise in obesity numbers and health concerns, planners and designers around the world are trying to bring back physical activity in day-to-day commuting behavior. Addressing health concerns through active transportation solutions not only brings us a step closer to a healthier community, but is also cost effective. Improving walking access to public transit stations is one such solution and was the theme of a paper published in the May issue of ITE journal.
In the study, researchers used the Sidewalk Availability and Quality Index (SAQI) and Connectivity Index (CI) to examine walking accessibility around ten bus rapid transit stations in Ahmedabad, India. These indices were first quantified and used by researchers from California in 2015 and were slightly modified to fit the Indian context. SAQI measures the availability and quality of sidewalks in a zone, whereas CI measures the density and connectivity of the roadway network. SAQI calculations, for a given area, use the length of a sidewalk, roadway functional classification, and quality based on the Likert scale, which is very much like the Level of Traffic Stress. CI uses intersection density and disparities in pedestrian access with different types of intersections.
For the Ahmedabad study, the researchers compared SAQI results with the Network Availability Index, which illustrates the full potential that an area has for sidewalk availability and quality within the existing street network, and compared CI with Potential Connectivity. These comparisons helped to assess the scope of improvement needed in order to get closer to the ideal conditions. The researchers also developed binomial regression models between the indices and ridership, with both indices showing a strong connection to ridership.
SAQI and CI can be very useful measures for quantifying potential walk access improvements, increasing public transit ridership, as well as planning new public transit stops. For a small area, and with the right resources, these indices can be calculated without the use of any expensive proprietary software.
Saumya Jain is a Senior Associate at SSTI.